Reference is made to co-pending U.S. application Ser. No. 07/778,409, filed Oct. 17, 1991, to Edward H. Cole, Jr., and Philip J. Mott, entitled "Single Pin Rocker Joint Chain," which is related to the subject matter of the present application, and is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to power transmission chains. More particularly, the present invention relates to a rocker joint for bushing chain or roller chain, which utilize a single pin. The invention has particular application to roller chains, which are used in engine timing applications as well as industrial applications. The invention also has application to silent chains, as well as chain-belts for use with continuously variable transmissions.
2. Description of the Prior Art
Power transmission chains are widely used in the automotive industry. Such chains are used for engine timing drives as well as for the transfer of power from the engine to the transmission or for the transfer of power in a transfer case. Power transmission chains are also widely used in industrial applications.
One type of power transmission chain is referred to as "silent chain". Silent chain is formed of interleaved sets of inverted tooth links. A set or rank of links is assembled from several links positioned alongside of or adjacent to each other. The links are connected by pivot means, which are typically round pins received in a pair of apertures. The pivot means may include a bushing inserted in one or both of the apertures of the links around the pins. An example of silent chain is found in U.S. Pat. No. 4,342,560, which is incorporated herein by reference.
A second type of chain is know as "roller chain". A typical roller chain consists of alternate inner links and outer links. The inner links, which are also known as "bushing" links, consist of spaced sidebars with bushings tightly received in openings, or apertures, at each end of the sidebars. The outer links, which are also know as "pin" links or guide links, consist of spaced sidebars with pins tightly received in openings, or apertures, at each end of the sidebars. The bushings freely rotate about the pins to pivotally connect the outer links to the inner links in alternate arrangement. Rollers are mounted for rotation about the bushings, and when the roller chain is wrapped about a sprocket, the teeth of the sprocket are received between the laterally spaced sidebars and the longitudinally spaced rollers. An example of roller chain is found in U.S. Pat. No. 4,186,617, which is incorporated herein by reference.
Roller chain drives can include both "true roller" and rollerless design. The true roller design includes the described rollers mounted about the bushings to contact the sprocket teeth. Rollerless chain contains bushings that directly contact the sprocket teeth. Both types of roller chain are typically specified in industry as British Standard chain and American National Standards Institute (ANSI) chain.
Another type of power transmission chain is used to transfer power between a pair of variable pulleys in a continuously variable transmission. The chain links are provided in sets that are interleaved together and have aligned apertures in the links that receive pivot means. Load blocks are positioned on the chain between the spaced pivot members and provide the means for transfer of power between the variable pulleys. The load blocks can be in the form of struts that are carried in a passageway below the links. Alternatively, the load blocks can extend around the links of the chain and have one or more windows for receiving the chain. The load blocks have tapered outer or end surfaces which engage the sheave faces of the pulleys to provide the driving engagement between the pulleys and the chain. Alternatively, the pivot members can directly engage the pulley sheaves. Examples of power transmission chains suitable for use in variable pulley transmissions, or continuously variable transmissions, are shown in U.S. Pat. No(s). 4,911,682, and 5,007,883, which are incorporated herein by reference.
The present invention relates to an improved rocker joint for power transmission chain, and particularly, for bushing silent chain or roller chain. Rocker joints are utilized in chains in an attempt to attain higher efficiencies and less wear than comparable round pin joints. Round pin joints typically produce higher wear as a result of the sliding action between the round pin and the inside of the circular link aperture. In contrast, rocker joints provide a lower wear joint on account of the rocking engagement between the pin and the rocker portion. The rocking engagement provides a rolling action between the pin and rocker, as contrasted with the sliding action between the pin and the aperture of the round pin joint.
Rocker joints for chains are known in the art. U.S. Pat. No. 4,186,617 discloses a rocker joint for a roller chain. Instead of bushings, the sidebars of both the inner links and the outer links have a second pin extending therebetween. The pins are placed side-by-side to define a pivot joint for the links. Each sidebar has an opening of generally circular configuration with a slightly pinched waist to divide the opening into two portions. The two pins are fitted into the opening to provide the rocker joint. Rollers are loosely mounted about the pins at each joint. The patent therefore describes a two-pin rocker joint for roller chain.
U.S Pat. No. 4,507,106 discloses a rocker joint in which, in the preferred embodiment, each pin or rocker has the identical cross-section. Each pin has a front surface which rocks on the front surface of the adjacent pin. In the preferred embodiment, the pins have a front surface defined by a first radius, and a back surface defined by a second and a third radius, both progressively smaller than the first radius. A rocker joint pair fits into each group of aligned apertures in the interleaved sets of links to join the links and permit articulation.
U.S. Pat. No. 4,911,682 discloses a rocker joint that includes a pair of pins. The rocker joint has apertures that are a generally hour-glass shape with the enlarged ends receiving the pins. The front surfaces of the pins rock against one another, while the back surfaces of the pins are prevented from substantial rotation.
These prior art patents represent examples of rocker joints utilizing two pivot members or pins, or a pin and a rocker pin. The present invention relates to single pin rocker joints. U.S. Pat. No. 2,667,791 discloses a silent chain with a single pin rocker joint. The chain has a single pin with an arcuate periphery, defined by a single radius, and a relatively flat bearing surface. The link has a generally semi-circular pin receiving aperture with an arcuate bearing surface. The flat surface of the joint pin rocks against the arcuate surface of the link aperture.
Another type of single pin rocker joint for silent chain is shown in U.S. Pat. No. 4,337,057. The patent discloses a double unrolling hinge for a chain-belt for a variable pulley transmission. Both sides of the hinge pin contact the insides of the link apertures.
The present invention, in its preferred embodiment, provides an improved single pin rocker joint for a chain in which a single pin rocks against a bushing aperture. The construction of the pin and rocker of the rocker joint has the pin disposed within the bushing aperture. The bushing aperture is formed to provide the rocker portion of the joint. The roller chain includes inner links and outer links and has use in engine timing drives. The present invention can also be adapted for use in silent bushing chain. The invention also has foreseeable use in chain drives for continuously variable transmissions.